Multi-functional fecal waste and garbage processor and associated methods

ABSTRACT

At least one aspect of the technology provides a self-contained processing facility configured to convert organic, high water-content waste, such as fecal sludge and garbage, into electricity while also generating and collecting potable water.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.16/361,115, filed Mar. 21, 2019, and titled MULTI-FUNCTIONAL FECAL WASTEAND GARBAGE PROCESSOR AND ASSOCIATED METHODS, which is a continuation ofU.S. patent application Ser. No. 15/629,642, filed Jun. 21, 2107, andtitled MULTI-FUNCTIONAL FECAL WASTE AND GARBAGE PROCESSOR AND ASSOCIATEDMETHODS, which is a divisional of U.S. patent application Ser. No.14/542,521, filed Nov. 14, 2014, and titled MULTI-FUNCTIONAL FECAL WASTEAND GARBAGE PROCESSOR AND ASSOCIATED METHODS, which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present technology is directed to multi-functional fecal waste andgarbage processing systems, equipment, and associated methods.

BACKGROUND

Many areas of the world utilize open sanitation systems for handlinghuman waste and other garbage, while other areas utilize unsatisfactoryseptic systems or other systems that discharge raw sewage into opendrains or surface waters. Such poor sanitation conditions contribute tosignificate health problems in these areas. Many of these areas withinadequate sanitation systems also struggle with maintaining cleandrinking water, which further adds to potential health issues. Theseareas often have limited resources available for generating electricity,or the cost for generating electricity is prohibitively expensive.Accordingly, there is a need for adequate sanitation systems that keepwaste out of the environment, for providing and maintaining access toclean potable water, and for generating inexpensive electricity.

SUMMARY

The present technology provides multi-functional systems for processingwaste while generating electricity and potable water in a manner thatovercomes drawbacks experienced in the prior art and provides additionalbenefits. At least one aspect of the technology provides aself-contained processing facility configured to convert organic, highwater-content waste, such as fecal sludge and garbage, into electricitywhile also generating and collecting potable water.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present technology can be better understood withreference to the following drawings. The components in the drawings arenot necessarily to scale. Instead, emphasis is placed on illustratingclearly the principles of the present technology. For ease of reference,throughout this disclosure identical reference numbers may be used toidentify identical or at least generally similar or analogous componentsor features.

FIG. 1 is a schematic flow-chart illustration of components of amulti-functional waste processing system in accordance with anembodiment of the present technology.

FIG. 2 is an isometric view of the multi-functional waste processingsystem of FIG. 1 .

FIG. 3 is an isometric view of a sludge holding and delivery system inaccordance with an aspect of the technology.

FIG. 4 is an isometric view of an in-feed assembly of an embodiment ofthe sludge holding and delivery system.

FIG. 5 is an isometric view of a sludge dryer assembly shown removedfrom the assembly of FIG. 2 .

FIG. 6 is an enlarged partial isometric view of an end portion of thesludge dryer assembly connected to a conveyor assembly of the in-feedassembly of FIG. 4 .

FIG. 7 is a schematic isometric view of the sludge flow duringprocessing in the sludge dryer assembly of FIG. 5 .

FIG. 8 is a partial isometric view of a sludge dryer assembly having asteam-heated auger rotatably positioned in a steam-heated trough thatcontains a flow of sludge.

FIG. 9 is an enlarged isometric view of the trough shown separated fromthe auger of FIG. 8 .

FIG. 10 is an enlarged isometric view of the auger shown separated fromthe trough of FIG. 8 .

FIG. 11 is a partial isometric view of a sludge dryer assembly ofanother embodiment having a steam-heated auger member rotatablypositioned in a steam-heated trough that contains a flow of sludge.

FIG. 12 is an enlarged isometric view of the steam-heated auger shownseparated from the trough of FIG. 11 .

FIGS. 13A and 13B are isometric views of a high-pressure, first-stagesludge dryer assembly in accordance with an embodiment of the presenttechnology.

FIG. 14 is a schematic flow chart of a two-stage sludge dryer system inaccordance with an embodiment of the present technology.

FIG. 15 is a schematic flow chart of a potable water treatment system ofthe waste processing system of FIG. 1 .

FIG. 16 is a schematic flow chart of a potable water treatment system ofanother embodiment of the waste processing system FIG. 1 .

FIG. 17 is an isometric view of a dry fuel bin assembly attached to thesludge dryer assembly of FIG. 5 .

FIG. 18 is an enlarged, partially transparent isometric view of the dryfuel bin assembly of FIG. 17 shown removed from the sludge dryerassembly.

FIG. 19 is a schematic side elevation view of dry fuel bin assembly ofFIG. 18 attached to a fluidized bed combustor in the system of FIG. 1 .

FIG. 20 is a partial cut away isometric view of a firebox and dischargebin of the fluidized bed combustor of FIG. 19 .

FIG. 21 is an enlarged isometric view of a combustion air compressor andin-line burner assembly shown removed from the firebox of FIG. 20 .

FIG. 22 is an enlarged isometric view of an air distribution grate shownremoved from the firebox of FIG. 20 .

FIG. 23 is an enlarged, partially cut away, isometric view of a dry fuelcombustor and boiler of the system of FIG. 1 showing the heated exhaustgas path through the boiler.

FIG. 24 is an enlarged partial isometric view of an economizer housingand multi-clone assembly shown removed from the dry fuel combustor ofFIG. 23 .

FIG. 25 is an enlarged partial isometric view of the economizer housingand an ash auger shown removed from the dry fuel combustor assembly ofFIG. 23 .

FIG. 26 is an enlarged, partially cut away, isometric view of the dryfuel combustor and boiler assembly of FIG. 23 showing the primary waterpath through the boiler.

FIG. 27 is a partially cut away isometric view of the piping componentsof a boiler of an alternate embodiment.

FIG. 28 is an isometric view of a fluidized bed combustor and boiler inaccordance with another embodiment, wherein modular boiler componentsare shown in open, exposed positions.

FIG. 29 is an isometric view of the fluidized bed combustor and boilerof FIG. 28 , wherein the modular boiler components are shown in stowed,operational positions.

FIG. 30 is an isometric view of a power plant assembly with a steamengine and generator shown removed from the system of FIG. 1 .

FIG. 31 is a partially cut away, enlarged top isometric view of theengine's head assembly with a camshaft, cams, rocker arms, and valvetrain in accordance with an embodiment of the technology.

FIG. 32 is an enlarged partial cross-sectional, isometric view of thesteam engine's head assembly of FIG. 31 with an intake cam, intake andexhaust valves, and associated rocker arms.

FIG. 33 is an enlarged cross-sectional of the steam engine's headassembly taken substantially along line 33-33 of FIG. 31 .

Appendix A includes additional information and calculations regardingaspects of the current technology.

DETAILED DESCRIPTION

The present disclosure describes multi-functional waste processingsystems configured for generating electricity and potable water inaccordance with certain embodiments of the present technology. Severalspecific details of the technology are set forth in the followingdescription and in FIGS. 1-33 to provide a thorough understanding ofcertain embodiments of the present technology. One skilled in the art,however, will understand that the present technology may have additionalembodiments and that other embodiments of the technology may bepracticed without several of the specific features described below.

FIG. 1 is a schematic flow-chart illustration of components amulti-functional waste processing system 10, and FIG. 2 is an isometricview of the waste processing system 10 in accordance with an embodimentof the present technology. As discussed in greater detail below, thesystem 10 is configured to receive and process a flow of wet wastesludge 12, and to generate dry, solid fuel material, electricity, andpotable water. One or more embodiments of the system 10 are discussedand illustrated herein in connection with processing waste comprisingwet sludge containing water and fecal matter and/or other garbage, suchas organic waste. The system 10, however, can be configured forprocessing a flow of other wet waste. In one embodiment, the system isconfigured to process wet sludge containing a mixture of water-basedliquids and up to approximately 50% total solids that can be separatedfrom the water and dried to provide combustible solid fuel material. Insome configurations, the system 10 can be used with wet sludge having upto approximately 15% total solids, and in other embodiments the system10 is configured for use with sludge having approximately 20%-50% totalsolids. The system 10 of other embodiments can be configured for usewith other ranges of total solids within the sludge.

The sludge 12 flows through a sludge dryer assembly 14 that evaporateswater from the sludge to generate steam, such that the solid materialsare sufficiently dried to provide combustible solid fuel material. Forpurposes of this description, the steam evaporated from the sludge isreferred to as sludge vapor. The liberated sludge vapor is very hot fora sufficient duration, so that the sludge vapor is sterile (i.e., freeof pathogens). The system 10 contains and condenses the sterile sludgevapor in a water treatment system 16 to provide clean potable water. Thesystem 10 also burns the dried solid fuel material, in a combustor, suchas a fluidized bed combustor 18. In some embodiments, other dried fuels,such as coal, wood pellets, garbage or other organic material can beadded if necessary to provide additional fuel to the combustor 18. Thesystem 10 of the illustrated embodiment is configured to continuallyproduce up to approximately 150 kW (approximately 200 hp) of electricityand to process approximately 8500 kg or 8.5 m³ of fecal sludge and 1100kg of garbage or more per day.

Heat from the fuel combustion in the combustor 18 is used to heat aboiler 20, which pressurizes water in a substantially closed primarywater circuit 21 to generate steam for use by a steam-driven power plant22 that produces electricity. The water in the primary water circuit 21is referred to as primary water, which may be primary steam or primaryliquid water, depending upon the location within the primary watercircuit. Primary steam exhausted from the power plant 22 which includesa steam engine 26 and a generator 25 is used as a heat source by thefuel dryer assembly 14 before the primary steam flows through acondenser 24 and is converted back to primary liquid water and pumpedback to the boiler 20. A portion of the electricity from the power plant22 powers electrical components of the system 10, and the remainingelectricity can be provided to a power grid or otherwise used locally,such as to power external electrical items.

The processing system 10 of the illustrated embodiment is aself-contained system that requires substantially no outsideelectricity, water or drainage to process the wet sludge and generateelectricity and potable water. In one embodiment, the illustrated system10 can be configured to occupy a volume with a footprint ofapproximately 15 m×3 m, which corresponds to a typical shippingcontainer, such that the system 10 may be transportable. Accordingly,the system 10 is well suited for use in a wide range of geographiclocations, such as under developed urban locations that may haveinadequate sewage systems, and that could benefit from additionalsources of electricity and clean, fresh potable water. The components ofthe system 10 of the illustrated embodiment are discussed in greaterdetail below.

Sludge Holding and Delivery System

The system 10 of the illustrated embodiment shown in FIG. 3 includes asludge holding and delivery system 30. The sludge holding and deliverysystem 30 has a holding tank 32 that receives substantially raw, wetsludge. The holding tank 32 can be sized to hold a selected volume ofwet sludge for continual operation of the system 10 for several daysbefore the holding tank 32 needs to be replenished. For example, in theillustrated embodiment, the holding tank 32 is designed to holdapproximately 30 m³ of wet sludge, which provides approximately threedays of operation, wherein the system 10 can process approximately 9-10m³ of sludge per day. The top of the holding tank 32 can be set close tothe ground to allow sludge delivery vehicles to easily empty the sludge12 into the tank. The bottom of holding the tank 32 can be sloped towardan outlet connected to a sludge in-feed assembly 34. In one embodiment,the in-feed assembly 34 can include a fully or partially enclosedconveyor 38, such as an auger or belt conveyor, that transports the wetsludge from the holding tank 32 to an inlet 40 of the sludge dryerassembly 14.

FIG. 4 is an isometric view of a sludge in-feed assembly 34 of anembodiment, wherein the holding tank 32 includes a drag-chain spreaderbox having an outlet 36 that deposits the wet sludge on the conveyor 38.The conveyor 38 extends upwardly at a selected angle relative to theground and connects to the sludge dryer assembly 14 adjacent to theinlet 40. In the illustrated embodiment, the conveyor 38 is slopedupwardly at an angle of approximately 30° relative to the ground,although other angles can be used in other embodiments.

Sludge Dryer Assembly

FIG. 5 is an isometric view of a sludge dryer assembly 14 shown removedfrom the assembly of FIG. 2 . The wet sludge transported from the sludgeholding and delivery system 30 (FIG. 3 ) is fed into a sludge inlet 40of the sludge dryer assembly 14. As seen in FIG. 6 , a sludge transitionauger 52 connected to the end of the conveyor 38 of the sludge in-feedassembly 34 feeds the wet sludge into the dryer, assembly's inlet 40 Theflow of sludge into the sludge dryer assembly 14 is substantiallycontinuous. FIG. 6 is an enlarged, partial isometric view of an endportion of the sludge dryer assembly 14 that includes the inlet 40. Inaddition to receiving the wet sludge, the sludge dryer assembly 14 alsoreceives primary steam exhausted from the steam engine 26 of the powerplant 22 (FIG. 1 ). The exhaust primary steam, which exits the steamengine 26 at approximately 207 kPa (approximately 30 psia), flows intoone or more tubular shells 42, each of which contains a tubular sludgecarrier 44. Heat from the exhausted primary steam boils the sludge inthe sludge carrier 44, thereby evaporating water from the sludge (togenerate sludge vapor), which dries the sludge to provide the solid fuelmaterial.

The sludge dryer assembly 14 of the illustrated embodiment includes twoenclosed large diameter pipes that each form a shell 42 that houses asmall diameter pipe forming a hollow sludge carrier 44. Each sludgecarrier 44 contains a rotatable, hollow auger 46, and the sludge carrier44 receives the sludge through the inlet 40 such that the sludge atleast partially surrounds the hollow auger 46. In the illustratedembodiment, each shell 42 includes a steam inlet 48 that receives theexhausted primary steam from the steam engine 26 (FIG. 1 ) such that thehigh-temperature primary steam flows into the shell's interior area andaround the sludge carrier 44, thereby heating the sludge in the sludgecarrier 44. Accordingly, the primary steam is physically isolated fromthe sludge while still being able to transfer heat to the sludge, whichboils the sludge and simultaneously cools the primary steam. Inaddition, a portion of the primary steam entering the sludge dryerassembly 14 flows into the interior area within the hollow auger 46 soas to also heat the sludge through the auger 46. In the illustratedembodiment, each hollow auger 46 is connected to a drive motor 47 thatrotates the auger 46 within the sludge carrier 44 and continuously movesthe wet sludge axially through the sludge carrier 44 as the sludge isdrying. In one embodiment, each drive motor 47 is a dedicated,five-horsepower, inverter-duty, three-phase electrical motor controlledby an independent variable frequency drive. Other embodiments can useother drive motors.

The two sludge carriers 44 are interconnected at their ends by transferhousings 50 that each have sludge passageways therethrough that allowthe sludge to flow axially through one sludge carrier 44 in onedirection, through the sludge passageway in the transfer housing 50, andaxially through the other sludge carrier 44 in the other direction.

FIG. 7 is a schematic isometric view of the sludge flow in the sludgedryer assembly from the inlet 40. As the sludge cycles through thesludge carriers 44, the water in the sludge is boiled off. When thesolid fuel material from the sludge is sufficiently dry, it exits thesludge dryer assembly 14 through one or more dried fuel outlets 54formed in the side of the sludge carrier 44 and corresponding shell 42.The dry fuel outlet 54 is sealed between the sludge carrier 44 and theshell 42 so as to maintain isolation of the sludge material from theprimary steam. In the illustrated embodiment, the dry fuel outlets 54are rectangular openings, although the dry fuel outlets can have othershapes (i.e., square, round, elliptical, etc.) and sizes.

In operation, the sludge level within the sludge dryer assembly 14increases as additional wet sludge is delivered into the sludge carrier44 by the transition auger 52 (FIG. 6 ). The solids within the sludgemoving through the sludge carrier 44 typically are sufficiently dried bythe time they reach the dry fuel outlets 54, and the sufficiently driedsolid fuel material spills out of the dry fuel outlet 54 and into a dryfuel hopper 56 (FIG. 2 ), discussed below. To ensure that the sludge ismoving through the sludge carrier 44 via the rotating hollow augers 46remains friable, an adequate amount of dried sludge will recirculateback into the beginning of the drying system adjacent to the inlet 40.Some of the sludge may be recirculated through the sludge assemblymultiple times before moving into the dry fuel hopper 56 (FIG. 2 ).

This recirculation of the drying sludge also prevents the sludge fromreaching a condition referred to as the “sticky” phase, wherein thesludge moisture content is about 0.3523 kg H₂O per kilogram of drymatter or 25% to 75% dry solid. Unlike in the “wet” or “paste” zoneswhere the sludge displays fluid-like properties, in the “sticky phase”the contact between the sludge and heated wall of the sludge carrier 44decreases dramatically, which negatively affects the evaporation rate.When the sludge is dried past the “sticky” phase to the “granular”phase, the drying sludge increasingly maintains homogeneous contact withthe heated wall of the sludge carrier 44, which allows the evaporationrate to return back to its original value. In addition to decreased heattransfer effectiveness, material in the “sticky” zone exhibitsconsiderable shear strength, such that the sludge material is morelikely to adhere to the rotating auger 46 rather than being conveyed byit. Recirculation of some dry sludge material helps to ensure that thecontents of the sludge dryer assembly always remain within or close tothe “granular” zone, thereby avoiding the “sticky” zone.

In the illustrated embodiment shown in FIG. 5 , the concentric tubulardesign of the sludge dryer assembly 14 is very durable. The dry fueloutlets 54, however, penetrate the sidewalls of the pressurized tubularshell 42, which may weaken the tubular structure. Accordingly, one ormore stiffening ribs 64 are attached to the shells 42 around the dryfuel outlets 54 to help maintain structural integrity and to keep thetubular structures from plastically deforming under the heat andpressure of the primary steam within the dryer assembly.

In addition to removing the dried solid fuel material from the sludgecarriers 44, the sludge vapor liberated from the sludge is removed fromthe sludge dryer assembly 14 through vapor outlet ports 66 incommunication with the interior area of each sludge carrier 44. Thesludge vapor flows from the vapor outlet ports 66 through conduits tothe water treatment system 16 (FIG. 1 ), which is discussed in greaterdetail below. In the illustrated embodiment, at least one vapor outletport 66 is provided at each end of the sludge dryer assembly, althoughthe outlet ports could be located at other positions.

As heat from the primary steam is transferred to the sludge, the primarysteam cools, such that the sludge dryer assembly 14 acts as a condenser,wherein the primary steam condenses within the shells 42 to primaryliquid water. The condensate remains isolated from the sludge and isremoved from the shells 42 by a condensate siphon tube assembly thatextracts the primary liquid water and directs it into one or moreprimary water lines 62 that carry the primary liquid water away from thesludge dryer assembly 14 along the primary water circuit 21 (FIG. 1 ).In the illustrated embodiment shown in FIG. 2 , the sludge dryerassembly 14 is mounted in the system 10 such that the shells 42 andsludge carriers 44 are tilted relative to horizontal, such asapproximately a 1-degree tilt, to facilitate extraction of the primarywater by the siphon tube assembly. The extracted primary liquid water isthen cycled back along the primary water circuit 21 for use by theboiler 20 and the steam engine 26 before returning again as steam to thesludge drying assembly 14.

FIG. 8 is a partial isometric view of another embodiment of a sludgedryer assembly 70 that includes a plurality of rotating and stationarypressure vessels heated by the exhausted primary steam up toapproximately 100 psig and 328° F. to mix and dry the sludge. Theillustrated dryer assembly 70 has a closed, sealed trough 72 containinga rotatable auger 74 that moves the sludge axially along the trough 72toward an outlet at one end of the trough 72. The trough 72 receives theflow of wet sludge through an inlet at one end such that at least aportion of the auger 74 is within the sludge. The trough 72 isillustrated in FIG. 8 without showing the lid or ends for purposes ofclarity to show the components within the trough 72. The lid and endsare sealed to the trough body 76 so as to fully contain the sludge andthe liberated sludge vapor during the drying process. In one embodiment,a hydraulically operated lid permits full and easy access to all of theinternal components of the sludge dryer assembly 70, as well as sealingall of the vapors, fumes, and gases within the trough 72. Accordingly,the sludge vapor and volatiles from the headspace in the trough 72 arecaptured and re-processed for purification (i.e., the water vapor)and/or re-combustion (i.e., the gases and/or volatiles).

FIG. 9 is an enlarged isometric view of the steam-heated trough 72 shownwith the auger 74 removed. The trough 72 contains a plurality ofstationary, spaced apart curved steam pipes 78 interconnected byelongated manifold pipes 80 that receive the high temperature exhaustedprimary steam from the steam engine 26 (FIG. 1 ) and evenly distributethe primary steam to the curved steam pipes 78. Accordingly, as thesludge enters the trough 72 near the inlet and moves along the trough 72via the auger 74, the sludge moves over at least a portion of the curvedsteam pipes 78, thereby boiling and drying sludge. By the time thesludge reaches the outlet at the end of the trough body 76 the sludge issufficiently dried. In addition, the primary steam condenses within thecurved steam pipes 78, and the condensate is collected in a returnmanifold pipe 82 connected to the primary water circuit 21.

FIG. 10 is an enlarged isometric view of the steam-heated, pressurizedauger 74 shown separated from the trough 72. The auger 74 has a hollowcentral shaft 84 that receives the exhausted primary steam. The auger 74also has a plurality of curved steam pipes 86 that communicate with theinterior of the central shaft 84 and extend radially in a spiral manneraway from the central shaft 84. Accordingly, the curved steam pipes 86receive primary steam from the central shaft 84.

The auger 74 is configured to rotate within the trough 72 so that thecurved steam pipes 86 pass through the spaces between the steam pipes 78in the trough 72. The auger's curved steam pipes 86 can be slightlyangled relative to the central shaft 84 so as to act as propulsionmembers that engage and push the sludge axially through the trough overthe curved steam pipes 78, thereby heating and boiling the sludge. Thehot primary steam in the central shaft 84 and in the curved steam pipes86 also heats the sludge, which results in the primary steam condensingwithin the auger 74. One end of the auger's central shaft 84 has acondensate outlet that directs the condensate out of the auger and alongthe primary water circuit 21 (FIG. 8 ) as primary liquid water. In theillustrated embodiment, the rotating auger 74 provides a mixing actionthat provides a self-leveling effect that causes the sludge to move fromone end of the trough 72 to the other. The auger 74 also meters thedried solid fuel material out of the dried fuel outlet. In at least oneembodiment, one or more dry fuel augers can be connected to the trough72 adjacent to the dried fuel outlet to carry the dried solid fuelmaterial to the dried fuel hopper 56.

FIGS. 11 and 12 are isometric views of another embodiment of the sludgedryer assembly 70 that has the trough 72 with the trough body 76, thecurved steam pipes 78, and the axially extending manifold pipes 80substantially similar to the sludge dryer assembly 70 discussed above inconnection with FIG. 8 . Accordingly, the trough 72 with the curvedsteam pipes 78 and manifold pipes 80 define a stationary pressure vesselheated by the primary steam. In this alternate embodiment, an auger 90is rotatably positioned within the trough 72 and driven by a drive motor92.

The auger 90 has a substantially hollow central shaft 94 connected to aplurality of hollow, straight finger pipes 96 that project radially fromthe central shaft 94. Each of the finger pipes 96 includes a support web98 secured to the central shaft 94 to provide additional strength andrigidity to the respective finger pipe 96 as the auger 90 rotates andthe steam-heated finger pipes 96 move through the sludge and slowly movethe drying sludge axially toward the dry fuel outlet. In one embodiment,the support webs 98 can also be angled relative to the central shaft'slongitudinal axis, and the support webs 98 may engage a portion of thesludge to facilitate mixing and/or to incrementally move the dryingsludge along the length of the trough 72.

For purposes of an example, the central shaft 94 of the auger 90 is arigid, 24-inch-diameter pipe operatively connected to approximately 140protruding 5-inch finger pipes 96 distributed around the pipe along itslength. The finger pipes 96 extend internally into the steam-filledcentral shaft 94 to ensure proper condensate removal upon condensationof the primary steam during operation. Each of the finger pipes 96 andassociated support web 98 are configured to accommodate the force of thedrive motor's full torque if that torque was fully applied to the end ofa single one of the finger pipes 96, while maintaining an actualmaterial stress below the material allowable stress for the auger'sdesigned pressure and temperature, such as approximately up to 100 psigand 328° F. In one embodiment, the finger pipes 96 are oriented in agenerally helically arranged pattern down the length of the centralshaft 94 in a configuration so no two finger pipes 96 initially engagethe sludge material at precisely the same moment, thereby evenlydistributing the impact loads throughout the auger's full rotation. Inaddition, neighboring planar finger pipe groupings are rotationallyoffset by approximately 45° to facilitate the sludge flow through thetrough 72 during the drying process.

As indicated above, the sludge vapor generated within the trough 72 isextracted through a vapor outlet. In one embodiment, the vapor outlet ispositioned adjacent to the trough's end panel that the sludge movestoward during the drying process. The sludge vapor removed from thetrough 72 flows into a water treatment system 16 where the sludge vaporis cleaned and collected, as discussed in greater detail below.

In one embodiment wherein the system 10 is used to process very wetsludge (e.g., sludge having a solid content of approximately 15% solidmaterials or less). The system 10 dries the wet sludge utilizing atwo-stage sludge dryer system that includes a high pressure first-stagedryer assembly 200 and a low pressure second-stage dryer assembly 220.FIGS. 13A and 13B are isometric views of a high-pressure first-stagedryer assembly 200 in accordance with an embodiment of the presenttechnology. The first-stage dryer assembly 200 includes an elongated,large diameter outer pipe 202 that contains a plurality of spaced apart,axially aligned scraper discs 204 structurally interconnected to eachother by one or more tie rods 205. For purposes of clarity for thisdiscussion, the outer pipe 202 is shown in FIGS. 13A and 13B asgenerally transparent to avoid obscuring the internal components fromview.

Each scraper disc 204 has a plurality of apertures 206 that axiallyalign with the apertures 206 in the other scraper discs 204. A pluralityof steam tubes 208 extend substantially along the length of the outerpipe 202 and through the aligned apertures 206 in the scraper discs 204.The scraper discs 204 also include bearings 209 that engage the insidesurface of the outer pipe. The ends of the outer pipe 202 are connectedto manifold portions 210 that communicate with the interior of the steamtubes 208. One of the manifold portions 210 (i.e., an inlet manifold 210a) has a steam inlet port 212 connected to the primary water circuit andconfigured to receive high temperature primary steam exhausted from thesteam engine 26 (FIG. 1 ). The primary steam flows from the inletmanifold 210 a into the steam tubes 208 within the outer pipe 202.

The outer pipe 202 has a sludge inlet port 211 that directs a flow ofvery wet sludge into the pipe's interior area such that the wet sludgedirectly engages the high temperature steam tubes 208. The structurallyinterconnected scraper discs 204 are connected to a reciprocating driveshaft 212 that sealably extends through the inlet manifold 210 a andconnects to an actuator 213, such as a hydraulic cylinder. The actuator213 is operable to push and pull the drive shaft 212, thereby moving thescraper discs 204 as a unit axially back and forth within the outer pipe202 and through the wet sludge. The high temperature primary steam inthe steam tubes 208 boils the water in the sludge to generate sludgesteam, thereby decreasing the water content of the sludge.

An elongate auger assembly 214 sealably extends through the inletmanifold 210 a and into the interior area of the outer pipe forengagement with the sludge. As the sludge thickens due to the waterevaporation, the auger assembly 214 helps move the thickened sludgethrough the outer pipe 202 to a sludge outlet port 215 at the end of theouter pipe 202 opposite the inlet port 211 of the dryer assembly 200.The extracted thickened sludge is then passed through a throttle 220 todecrease the pressure and directed into the second-stage dryer assembly220 (FIG. 14 ), discussed in greater detail below.

As the primary steam in the steam tubes 208 heats and boils the wetsludge, the primary steam condenses and the resulting primary liquidwater flows out of the steam tubes 208 into a collection area in theoutlet manifold 210 b. The primary liquid water flows out of thecollection area through a primary water outlet port and into a conduitcoupled to a radiator 190 (discussed below) that cools the liquid waterin the primary water circuit 21. The sludge vapor liberated from thesludge is heated and maintained a high temperature during the dryingprocess, which results sterilizing the sludge vapor while in the outerpipe 202. As seen in FIG. 14 , the sludge vapor is extracted from theouter pipe 202 through a recovery port 216 and into a sludge vaporoutlet conduit 218 that carries the sludge vapor to the water treatmentsystem 16. The sludge vapor is then filtered via a cyclone, one or morepre-filters (˜25 micron filter), and one or more fine filters (˜1micron). The filtered, sterilized sludge vapor is then directed into thesecond-stage dryer assembly 220.

In the illustrated embodiment, the second-stage dryer assembly 220 issubstantially identical to the sludge dryer assembly of FIGS. 8-10 orFIGS. 11-12 , except that the high temperature steam that passes intothe curved steam pipes 78 in the trough 72 and into the rotating auger74 or 90 is the filtered, sterilized sludge vapor from the first-stagedryer assembly 200 (FIG. 13 ), rather than the high temperature primarysteam from the steam engine. In this embodiment, the heat from thefiltered, sterilized sludge vapor from the first-stage dryer assembly200 is used to dry the fecal sludge in the second-stage dryer assembly220. Accordingly, this two stage sludge dryer system allows twice asmuch sludge to be processed with substantially the same amount ofprimary water.

After the heated, pressurized sludge vapor flows through the curve pipes78 and/or the auger 74/90, and the sludge vapor condenses. The resultingcondensate extracted from the return manifold pipe 82 and from theauger's hollow central shaft 84 flows to the water treatment system 16.In addition, the drying process within the second-stage dryer assembly220 boils water out of the drying fecal sludge, and that sludge vaporexits the trough 72 of the dryer assembly 70 and flows to the watertreatment system 16 (FIG. 15 ).

Water Treatment System

FIG. 15 is a schematic flow chart of the water treatment system 16. Thesludge vapor flows into a steam filtration system 100 that includes acyclone, which separates the steam from other particulates that may bein the sludge vapor. The separated sludge steam is then passed throughone or more pre-filters, such as a large pore filter (i.e., a 25 micronfilter), and then through a fine steam filter (i.e., a 1 micron filter).The filtered sludge steam then flows to the condenser 104 that condensesthe sludge steam and collects the resulting sterile liquid water. Whilethe filtered sludge steam and the resulting condensed water may includesome impurities, the filtered steam and condensed liquid water ispathogen free because the sludge vapor was exposed to very hightemperature long enough to kill any pathogens in the sludge vapor.

The sterile water is then purified by an aeration process, then ableaching process, and then a filtration process through selectedpurification filter, such as one or more charcoal filters. The purified,clean, potable water is then captured in a clean water storage tank 108,from which the clean water can be dispensed.

FIG. 16 is a schematic flow chart of the water treatment system 16 inconnection with an embodiment using the two-stage dryer assembly. Inthis embodiment, the high-pressure sludge vapor from the first-stagedryer assembly 200 flows through a water treatment system 16 and isfiltered, as discussed above, and then used in the second dryer stageassembly 220. The condensate from that sludge vapor in the second dryerstage assembly 220 is collected and passed through the water treatmentsystem 16 where it is purified via the aeration, bleaching, andfiltration processes, as discussed above. The sludge vapor from thesecond-stage dryer assembly 220 entering the water treatment system 16is also filtered (i.e., with the cyclone, pre-filter, and fine filter),condensed, and the resulting condensate is purified and collected in thestorage tank 108.

Dried Solid Fuel Handling System

Returning now to the dried solid fuel material, as it exits the sludgedryer assembly 14/70/200/220 as discussed above, dried solid fuelmaterial enters the dry fuel hopper 56. FIG. 17 is an isometric view ofa dry fuel hopper 56 attached to the sludge dryer assembly 14 adjacentto the stiffening ribs 64. FIG. 18 is an enlarged, partially transparentisometric view of the dry fuel hopper 56 shown removed from the sludgedryer assembly 14. The dry fuel hopper 56 of the illustrated embodimentincludes a bin that receives the dried solid fuel material through anopen top side. A heating coil 110 is attached to the side of the bin andheats the bin to ensure no condensation of liquid water from any sourcegets to the dried solid fuel material. The heat from the heating coil110 can also further drive the solid fuel material. In one embodiment,the fuel bin heating coil 110 can be a steam coil that receives aportion of the sludge vapor generated by the sludge dryer assembly 14(FIG. 17 ), such that the contents of the bin are preheated to aboveapproximately 120° C. (240° F.).

In the event that water or moisture somehow get into the hopper 56 andsoaks the dried solid fuel material, or if that the dried fuel solidmaterial is too wet to efficiently burn, then the hopper 56 will need tobe emptied. Accordingly, the hopper 56 includes a wet fuel out-feedauger 115 that will direct the wet fuel back to the wet sludge holdingtank 32 (FIG. 1 ).

As seen in FIGS. 18 and 19 , the hopper 56 of the illustrated embodimentincludes a dry fuel conveyor 112 coupled to the bottom of the hopper'sbin. The conveyor 112 is connected to a fuel in-feed auger assembly 114that carries the dried solid fuel material to the firebox or fluidizedbed 116 of the combustor 18 (FIG. 19 ), wherein the dried solid fuelmaterial is burned in a suspension of sand particles. In the illustratedembodiment, the in-feed auger 114 feeds the dried solid fuel materialinto the fluidized bed combustor 18 approximately 12 cm (4.5 in.) abovethe fluidized bed 116 and at approximately the same height as a flow ofcombustion air received from a combustion fan, discussed in greaterdetail below. While the illustrated embodiment utilizes a dry fuel feedauger assembly 114, other fuel delivery systems need be used, includinga gravity fed system, or other pain systems to provide the solid fuelmaterial into the combustor.

In one embodiment, the waste processing system 10 (FIG. 1 ) can includean auxiliary dry fuel hopper 118 (FIG. 1 ) containing auxiliary fuel,such as coal, wood pellets, organic garbage, or other suitable dry fuelthat can be burned in the fluidized bed combustor 18 along with thedried solid fuel material if needed. The auxiliary dry fuel hopper 118also includes an in-feed auger 120 (FIG. 19 ) connected to the combustor18 for delivery of the auxiliary fuel to the fluidized bed 116 forcombustion. The in-feed auger 120 can also be used to add sand,limestone, or other selected bed material to the fluidized bed 116 ofthe combustor 18.

Combustor Assembly

As shown in FIG. 19 , the fluidized bed combustor 18 is connected to thelower portion of the boiler 20 so as to burn the dried solid fuelmaterial and heat the boiler 20. The combustor 18 of the illustratedembodiment has a firebox 122 that houses the fluidized bed 116 andassociated heat transfer equipment. FIG. 20 is a partial cut awayisometric view of the firebox 122, which is connected to an ashdischarge bin 126 by a discharge auger 128. FIG. 22 is an enlargedisometric view of the air distribution grate 130 shown removed from thefirebox 122. The illustrated air distribution grate 130 is configured tofluidize the bed 116 in a homogeneous and stable manner, and it suppliesthe primary combustion air for the burning process within the combustorassembly 18. The illustrated fluidized bed 116 comprises sand, althoughlimestone or other suitable materials, or mixtures thereof may be used.The air distribution grate 130 is configured to operate for long timeperiods without warping, braking, or plugging. The air distributiongrate 130 is also integrated into the firebox 122 in a manner allowingit to be easily and quickly replaced or repaired to minimize any downtime of the combustor 18 and the associated system 10.

The air distribution grate 130 includes an insulated air distributionpipe 140 with an air inlet 142 and a plurality of sparger-type airmanifold tubes 144 connected to the air distribution pipe 140 downstreamof the air inlet 142. The manifold tubes 144 are parallel and spacedfairly close to each other to allow ash and small sand particles toeasily fall between the manifold tubes 144 for removal by the dischargeauger 128 to the discharge bin 126 (FIG. 20 ). The spaced apart manifoldtubes 144, however, prevent clinkers and large unburned material fromdropping into the discharge auger inlet. Each manifold tube 144 isconnected to a plurality of bubble cap air nozzles 146 distributed in agrid format. The bubble cap air nozzles 146 provide smooth and even airdistribution into the freeboard portion above the bed 116 forhomogeneous fluidization in the firebox.

In the illustrated embodiment shown in FIG. 21 , the air distributiongrate 130 is connected to an in-line burner assembly 138 that can beactivated to preheat incoming combustion/fluidization air as needed,such as during initial startup and warm up of the fluidized bed 116(FIG. 20 ). The in-line burner assembly 138 includes a shrouded heater150 that receives a flow of air from a combustion fan 148. The heater150 is connected to the air inlet 142 of the air distribution pipe 140(FIG. 22 ) to provide the combustion air to the fluidized bed 116 viathe air distribution grate 130 (FIG. 20 ). The combustion fan 148 of theillustrated embodiment provides air at an approximate flow rate of up to750 ft³/min compressed to approximately 50 in. H₂O. The heater 150 canrun on natural gas, propane, butane, or other suitable fuel to preheatthe combustion air when needed. Once the combustor 18 has warmed upclose to operational temperature, the in-line burner assembly 138 is nolonger needed, and the combustion fan 148 provides the unheated air tothe fluidized bed 116 for combustion with the solid fuel material.

Boiler

The combustor assembly 18 is positioned within the boiler 20, and theheat generated upon burning the dried solid fuel material provides acontinuous flow of heated exhaust gas that flows through the boiler 20along an exhaust gas path 158 (FIG. 23 ) and boils a continuous flow ofprimary liquid water flowing generally in the opposite direction throughthe boiler 20 along a primary water path 160 (FIG. 24 ) to produce highpressure steam that will power the steam engine 26 (FIG. 1 ). The boiler20 and its components will be discussed in connection with the exhaustgas path 158 (FIG. 23 ) and then in connection with the primary waterpath 160

FIG. 23 is an enlarged, partially cut away, isometric view of the dryfuel combustor 18 and the boiler 20 showing the heated exhaust gas path158 through the boiler. A lower portion of the boiler 20 includes anevaporator 162 embedded at least partially in and positioned immediatelyabove the fluidized bed 116. Accordingly, the high-temperature heatgenerated from burning the solid fuel material in the fluidized bed 116flows around and efficiently heats the evaporator 162. The exhaust gaspath 158 flows upwardly from the evaporator 162, over a primarysuperheater 164 connected to the evaporator 162, and then over asecondary superheater 166 connected to the primary superheater 164. Theexhaust gas path 158 flows from the secondary superheater 166 over aprimary economizer 168 and then over a secondary economizer 170. Theheated exhaust flowing along the exhaust gas path 158 cools as ittransfers heat sequentially to each of the evaporator 162, the primarysuperheater 164, the secondary superheater 166, the primary economizer168, and the secondary economizer 170. The secondary economizer 170 iscontained in an economizer housing 172 and connected to an exhaustoutlet 174. By the time the exhaust gas reaches and flows over thesecondary economizer 170, the exhaust gas transfers only low grade heatto the secondary economizer 170 before exiting the exhaust outlet 174.

FIG. 24 is an enlarged partial isometric view of the economizer housing172 and a multi-clone assembly 176 connected to the exhaust outlet 174.The exhaust gas enters the multi-clone assembly 176 and flows throughone or more conventional cyclones to remove any remaining ash orparticulates from the exhaust flow, thereby providing clean exhaust gasthat exits the multi-clone assembly 176. The exhaust gas can also bebubbled through a chemically treated water column to remove anyadditional contaminates before being released to the atmosphere. Thesubstantially particulate free exhaust gas exits the multi-cloneassembly 176 and flows through an exhaust stack 178 open to theatmosphere. In the illustrated embodiment, an induced draft fan 180 ispositioned between the multi-clone assembly 176 and the exhaust stack178 and is configured to facilitate flow of the exhaust gas along theentire exhaust gas path 158 and out the exhaust stack 178. In theillustrated embodiment, the fan 180 is capable of pulling approximately8 inches of H₂O vacuum at a flow rate of approximately 775 scfm,although other embodiments can use other fans or exhaust draw systemsfor controlling the flow and rate of exhaust gas along the exhaust gaspath 158.

FIG. 25 is an enlarged partial isometric view of the economizer housing172, which has an ash collection area 182 in the bottom of the housingand an ash auger 184 connected to the ash collection area 182. By thetime the exhaust gas enters the economizer housing 172, the exhaust gashas substantially cooled, and any heavier ash particles that may beflowing with the exhaust gas will drop into and collect in the ashcollection area 182. The ash auger 184 is configured to carry thecollected ash away from the economizer housing 172 and into a collectionbin or other collection system (not shown).

Primary Water Circuit Prior to Boiler

Turning now to the primary water path 160, the flow of primary waterenters the boiler 20 in the liquid phase. As discussed above inconnection with the sludge dryer assembly 14, the primary water flowfrom the steam engine 26 is condensed in the sludge dryer assembly tothe liquid phase. In the illustrated embodiment shown in FIG. 1 , theflow of primary liquid water from the sludge dryer assembly 14 can passthrough a radiator 190 to help cool the primary liquid water prior tocontinuing along the primary water circuit 21.

As the primary water (sometimes referred to as “feedwater”) movesthrough the primary water circuit 21 in the steam/vapor and liquidphases, some of the primary water may be lost. For example, some primarywater may be lost by steam blowing by in the steam engine 26 whereinsteam blows past the piston along the cylinder walls in the engine. Inaddition, some of the primary water may be removed from the system 10and discarded at the lowest point in the system 10 to remove any usedchemicals or minerals that may have precipitated out of the primarywater, which is referred to as blowdown. Depending upon the waterquality and the system 10, blowdown can constitute up to approximately5% of the total flow of the primary water. Accordingly, makeup water canbe added to the primary water circuit 21 via a water conditioner 192located downstream from the radiator 190.

The water conditioner 192 can also add chemicals or additives to theprimary water while in liquid phase. In some embodiments, the chemicalsand/or additives are added to the makeup water introduced into theprimary water circuit 21. For example, the makeup water may be softenedvia chemical additives prior to entering the primary water circuit toreduce scaling of the pipes in the boiler 20. Chemical additives mayalso be used to minimize impurities and corrosion products, which cannegatively impact heating efficiencies or can potentially shorten theoperational life of the conduits through which the primary water flowsin the primary water circuit 21. In addition, the water conditioner 192can be used to treat incoming water, which may be hard public water,prior to the makeup water being added into the primary water circuit 21.

The primary water flows from the water conditioner 192 and is collectedin a feedwater tank 194 before the primary liquid water is introducedinto the boiler 20. The feedwater tank 194 can include a level switch sothat after the primary liquid water is returned, the system has a way ofmeasuring and adding the appropriate quantity of makeup water andchemicals to account for any losses in the primary water circuit 21. Theprimary liquid water is drawn from the feedwater tank 194 by a feedwaterpump 196 that pumps the primary liquid water into the boiler 20.

Primary Water Path in Boiler

Returning now to the boiler 20, FIG. 26 is an enlarged, partially cutaway, isometric view showing the primary water path 160 through theboiler 20. The primary liquid water received from the feedwater pump 196(FIG. 1 ) is introduced as cold pressurized water into the boiler 20through a water inlet 198 adjacent to the secondary economizer 170. Thecold primary water from the pump 196 is pressurized to approximately4130 kPa (600 psia), and it flows through the secondary economizer 170,which is heated by the exhaust gas at the coolest portion of the exhaustgas path 158 (FIG. 23 ) within the boiler 20. In the illustratedembodiment, the secondary economizer 170 heats the primary liquid waterto its saturation point, which is approximately 525K at 4.135 MPa.

The primary water flows from the secondary economizer 170 through theprimary economizer 168, wherein the primary water is heated to itsboiling point. The primary water flows out of the primary economizer 168as steam and into a steam drum 199, wherein the dry, saturated steam isseparated from any saturated liquid. Any saturated liquid in the steamdrum 199 is returned and reintroduced into the evaporator 162. The dryprimary steam flows out of the steam drum 199 and sequentially throughthe secondary and primary superheaters 166 and 164. The primary steamexits the primary superheater 164 as high-temperature, superheatedsteam, which flows out of the boiler 20, along the downstream portion ofthe primary water path 160 to the steam engine 26.

Although the boiler 20 illustrated in FIGS. 23 and 26 includes twosuperheaters 164/166 and two economizers 168/170, the boiler 20 of otherembodiments may include only one superheater and/or only one economizer.For example, FIG. 27 is a partially cut away isometric view of thepiping components of a boiler assembly 222 of an alternate embodimentthat includes only one superheater 224 and one economizer 226 coupled tothe evaporator 228 and the steam drum 199. In this alternate embodiment,the steam drum 199 is connected to a plurality of vertical pipes thatform waterwalls 232 on opposing sides of the evaporator 228, which helpsto shield the evaporator, the fluidized bed 116, and the firebox 122, toretain heat between the waterwalls, and to help heat the saturated waterflowing through the waterwalls 232. Accordingly, use of the waterwalls232 helps to eliminate or decrease the amount of refractory materialneeded within the boiler.

FIGS. 28 and 29 are isometric views of a boiler 240 in accordance withanother embodiment. The boiler 240 has a component layout similar toFIG. 27 , wherein one superheater 224 and one economizer 226 arepositioned alongside the evaporator 228, which allows for significantlymore freeboard within the evaporator section above the fluidized bed116. This embodiment also includes the waterwalls 232 extending from thesteam drum 199. In addition, the boiler 240 has a housing 241, and thesuperheater 224, the economizer 226, and the evaporator 228 are eachmounted on frame structures 242 movably carried on one or more rails orsliders 244 connected to the housing 241.

Each frame structure 242 and its respective boiler components (i.e.,superheater 224, economizer 226, and/or evaporator 228) is movable as aunit relative to the housing 241 in a translatable manner analogous to adrawer motion between an open, exposed position (FIG. 28 ) and a closed,operational position (FIG. 29 ). Any or all of the superheater 224, theeconomizer 226, and/or the evaporator 228 can be moved to the open,exposed position in a modular manner, such as for maintenance orreplacement when the system 10 (FIG. 1 ) is not running. Before theboiler components can be moved to the open, exposed position, some ofthe interconnecting piping defining the primary water path 160 may needto be disconnected. The superheater 224, the economizer 226, and/or theevaporator 228 can be slid back into the housing 241 and to the closedoperational position, and the interconnecting piping reconnected. Thismodular approach can greatly decrease potential down time of the system10 as well as the cost for conducting regular maintenance of the boiler240.

In another embodiment, the boiler 20 can be a concentric boiler having acentral combustion chamber and fluidized bed. A generally cylindricalevaporator is coaxially arranged with the combustion chamber, and thesuperheater and the economizer are concentrically disposed radiallyoutward of the evaporator. Other embodiments can utilize boilers withother configurations and/or components and/or component arrangements.

Power Plant

FIG. 30 is an isometric view of the power plant assembly 22 with agenerator 28 driven by the steam engine 26. In the illustratedembodiment, the generator 28 is a 175 kW induction generator with anoperational output of up to approximately 150 kW (200 hp). Theelectricity produced from the generator 28 is utilized to power anyparasitic loads, including the air blower, all of the pumps, the motorsthat turn the augers, etc. The excess electricity can be made availablefor local use or provided to a selected power grid.

The steam engine 26 driving the generator 28 receives the superheatedprimary steam from the boiler 20 (FIG. 1 ), and the primary steam isexpanded in the engine to approximately 207 kPa (˜30 psia). The steamengine is a multi-cylinder reciprocating piston engine with a headassembly 300 configured to use the hot steam at a temperature of up toapproximately 480° C. (900° F.) and to operate for long durations athigh pressures, such as approximately 4130 KPa (600 psia). In theillustrated embodiment, the engine 26 is a six-cylinder engine, althoughother engines, such as a V-8 reciprocating piston engine, may be used.

FIG. 31 is a partially cut away enlarged top isometric view of theengine's head 301 removed from the block. The illustrated head assembly300 includes a head 301 made of steel and that includes a steam inletport 302 for each cylinder. The steam inlet ports are positionedgenerally on top of the cylinder head. The head assembly 300 includes avalve train 304 with poppet valves 306 and associated rocker arms 308for each cylinder. A camshaft 310 has a plurality of precisely contouredcams 312 for each of the intake and exhaust poppet valves 306 a and 306b. Rotation of the camshaft 310 and the associated cams 312 controls theopening and closing of the intake and exhaust valves 306 a and 306 b forthe specific operating parameters of the steam engine 26.

The reciprocating steam cycle of the steam engine 26 consists of fourdistinct events taking place over two strokes of the engine's pistonwithin its cylinder. Starting at Top Dead Center (TDC), the cylinder'sintake valve 306 a opens and the superheated, high-pressure steam(received from the boiler) flows through the steam inlet port 302 andinto the cylinder while the piston moves downwardly toward Bottom DeadCenter (BDC). At a specified cut-off volume of steam, the intake valve306 a closes and the piston completes the power stroke to BDC. At BDCthe exhaust valve 306 b opens, and the exhaust stroke begins as thepiston moves upwardly toward TDC. At a specified time before TDC, theexhaust valve 306 b closes so the cylinder pressure rises close to theboiler pressure. This minimizes the throttling losses when the intakevalve 306 a opens.

As the steam engine 26 of the illustrated embodiment is operating withsteam based on a boiler pressure of approximately 4130 kPa (600 psia),the intake and exhaust valves 306 a and 306 b must be carefullycontrolled via precise cam profiles and valve train arrangement tomaximize the engine's efficiency and power for the given boiler pressureand the engine torque limits. In the illustrated embodiment, at a boilerpressure of approximately 4130 kPa (600 psia), the cut off ratio foreach cylinder (i.e., the ratio of the cutoff volume to the total volumeof the cylinder) is approximately 11%. Accordingly, the intake valve 306a must be opened just long enough to fill 11% of the cylinder with thehigh-pressure primary steam. The steam engine 26 (FIG. 30 ) isconfigured to provide a clearance volume of approximately 17.7 cc ratherthan a typical, conventional clearance volume of approximately 70 cc foran engine with a compression ratio of approximately 9.8. This clearancevolume of 17.7 cc provides 28° of crankshaft rotation to achieve thedesired cut off ratio of 11%. Because the camshaft 310 rotates twice asfast as the crank shaft, the camshaft 310 and cams 312 must open andclose each intake valve 306 a within 14° of revolution. This quickmotion is controlled by the cam profiles and the intake valve 306 aconfiguration.

FIGS. 31 and 32 are enlarged cross-sectional views of the head assembly300 showing an intake cam 312 a, the intake valve 306 a, and associatedrocker arm 308 a. Given that the cutoff ratio for the engine of theillustrated embodiment is only 11%, the cam profile for each intake cam312 a includes extremely small lobes 314 configured to quickly andprecisely pivot the respective rocker arm 308 a to open and close theassociated intake valve 306 a. This small lobe shape must have fairlysteep transition areas 316 on the cam profile, which creates asubstantially concave, small-radius curve that the cam follower 318 mustfollow. In the illustrated embodiment, the cam follower 318 is a rollingcam follower rotatably carried by a pair of bearings 320 within therocker arm 308 a above the respective intake cam 312 a. This arrangementof the rolling cam follower 318 and bearings 320 in the rocker arm 308 aallows the cam follower 318 to handle the inertial loads duringoperation of the engine 26.

As shown in FIG. 33 , when the intake valve 306 a is closed, its valvehead 319 sealably sets on top of a valve seat 321 in the head 301, andthe steam inlet port 302 to delivers the primary steam above the intakevalve 306 a (i.e., on top of the valve head). The valve train 304 isconfigured with the cam follower 318 positioned vertically above itsrespective cam 312, and the cam follower 318 is spaced apart from therocker arm's pivot pin 322. Also, the distal end of the rocker arm 308is positioned under and engages the bottom surface of a collar 324threadably attached to the top of the intake valve's shaft 326. When theintake cam 312 a rotates and the cam follower 318 engages the small lobe314, the rocker arm 308 pivots upwardly about the pivot pin 322 andpulls the intake valve 306 a upwardly to lift the valve head 319 awayfrom the valve seat 321, thereby briefly opening the intake valve 306 a.Accordingly, the intake valve 306 a is a pull poppet valve. As the cam'slobe 314 passes the cam follower 318, the intake valve 306 a is quicklyclosed. Unlike intake valve 306 a, the exhaust valve 306 b does notrequire such quick, responsive action and can be a push poppet valve.

The illustrated cylinder head configuration is such that the hot,high-pressure steam is on top of the cylinder head, and the inlet valve306 a needs to be on the same side as the high-pressure steam, otherwisethe inlet valve 306 a would open by the steam pressure. As the inletvalve's position is on the top of the head below the steam inlet port402, the high-pressure steam holds the intake valve 306 a closed. In theillustrated embodiment, the intake valve 306 a is connected to a spring328 that provides additional forces to help lift and open the intakevalve to let steam into the cylinder as the piston moves from TDC untilthe achieving the cutoff volume (˜11%).

The configuration of the steam engine 26 of the illustrated embodimentalso provides improved temperature control of the engine duringoperation, particularly at high RPMs (i.e., ˜1850) over very long timeperiods. Unlike conventional steam engines that use double actingcylinders with steam pressure applied alternately to either side of thepiston and exhausted on either side of the piston, the steam engine 26of the illustrated embodiment has single acting cylinders. To avoidsteam leaking around the piston particularly at low operatingtemperatures (i.e., during start up), the current engine 26 utilizesliquid coolant built into the engine with both a radiator and heater tocontrol the temperature of the engine. When the engine 26 is startingand not yet warmed up, the heater keeps the engine's cylinders wellabove water's boiling temperature, so the steam will not condense.Because the high-pressure steam is hot, once the engine is running, thetemperature control system is in a cooling mode. Accordingly, thetemperature control system carefully controls the engine temperature andprevents the engine 26 from getting too hot, which would damage the oil,and from getting too cold (i.e., below approximately 160° F.), whereinthe oil in the crank case and any water that gets past the piston viablow-by would mix and form an emulsion that would be impossible toseparate.

Controls

The fecal sludge waste processing system 10 of the illustratedembodiment also includes a plurality of automated, integrated,computerized controls interconnected and configured for control of theentire system 10 with only minimal supervision from an operator, duringnormal operation. Control and monitoring of the equipment and processesare accomplished primarily through a central programmable logiccontroller (PLC) that collects inputs from sensors and sets outputlevels for the control devices, such as the valves and motors. The PLCis also configured to control operation of specialty controls for theelectric generator system and propane burner used during startup. ThePLC is also configured to divide the overall system into manageablesubsystems, such as clean water/steam, combustion, fuel handling, andpower generation. Control inputs are provided to decouple subsystemsfrom each other to the extent desired. The subsystems can be furtherdivided into control loops to provide set points for individual outputs.

The clean water/steam subsystem is configured to provide steam at aconstant temperature and pressure to power plant 22, and to provide heat(in the form of steam) to the sludge dryer assembly 14 for generatingsufficiently dry solid fuel. Control loops are used to regulate thequantity of makeup water entering the system, the condensate quantityentering the evaporator, the quantity of steam bypassing the steamengine, and the heat applied to the sludge drying assembly. The cleanwater/steam system is also configured to monitor and treat any externalwater entering the system, such as city water, and to control the totaldissolved solids content of the boiler water through a blowdown system.

The combustion subsystem is configured to provide sufficient heat tokeep the clean water/steam system producing the correct amount andtemperature of steam. Control loops are provided that regulate the airflow through the fluidized bed, to operate the propane burner duringstartup, and to control the air pressure in the combustion chamber. Thissystem will also monitor combustion emissions and exhaust gas handlingand maintenance tasks, such as removal and fluidized bed materialreplacement.

The fuel handling subsystem is configured to provide the correctquantity of dried fuel to the combustion process and handle the wastewater generated from the drying process. Control loops are used toprovide the correct quantity of wet fuel, to regulate the dwell time ofthe solid fuel material in the sludge dryer assembly, to meter the driedsolid fuel material into the combustor, and to handle the watercondensation and treatment process.

The power generation subsystem is configured to provide power to thegrid when available. This subsystem has control loops that regulate theelectrical power output and regulate the engine speed and torque throughmodulation of the engine throttle. The control subsystems and low levelloops can be integrated into a higher level controller to handle startupand shutdown sequences and to handle emergency and alarm situationsappropriately.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from theinvention. Additionally, aspects of the invention described in thecontext of particular embodiments or examples may be combined oreliminated in other embodiments. Although advantages associated withcertain embodiments of the invention have been described in the contextof those embodiments, other embodiments may also exhibit suchadvantages. Additionally, not all embodiments need necessarily exhibitsuch advantages to fall within the scope of the invention. Accordingly,the invention is not limited except as by the appended claims.

I claim:
 1. A method of processing wet organic sludge having water andsolid fuel material, comprising: Directing a flow of the sludge along afuel path of a fuel dryer assembly, wherein the sludge moves through aheater portion of the fuel dryer assembly; boiling the sludge in thefuel dryer assembly with heat from the heater portion and thermallyseparating the water from the solid fuel material to provide dried fuel;condensing in a fresh water condenser assembly steam liberated from thesludge for use as potable water; receiving in a dry fuel combustorassembly the dried fuel from the fuel dryer assembly, the dry fuelcombustor assembly having a combustor portion and having a boilerconfigured to receive heat from the combustor portion; directing steamfrom the boiler to a fluid path of a condenser portion of the fuel dryerassembly, wherein the fluid path through the condenser is isolated fromthe fuel path; combusting the dried fuel in the combustor portion togenerate heat that boils water in the boiler to generate steam;generating electricity with a steam powered generator via the steamreceived from the boiler, the steam powered generator providing steam tothe condenser portion; directing the condensed steam from the freshwater condenser assembly through a water treatment system that receivesthe condensed steam in either vapor phase or liquid phase or both,wherein the condensed steam as liquid water is passed through a purifierand filter to provide the potable water; and pumping with a water pump aflow of water from the condenser portion of the fuel dryer; wherein theflow of water is pumped from a water outlet of the water pump to theboiler; wherein the boiler converts a flow of water entering the boilerto a flow of steam to power the steam-powered generator.
 2. The methodof claim 1, further comprising moving and heating the sludge in the fueldryer with a heated auger in the fuel carrier during the drying process.3. The method of claim 1 wherein the fuel dryer is a two-stage dryerhaving sequential first and second dryer stages each coupled to thecondenser portion and the sludge in each of the first and second dryerstages is dried by evaporating water from the sludge using heat fromexhaust steam from the steam-powered generator.
 4. The method of claim3, further comprising generating with the first dryer stage sludge steamfrom the sludge, and using in the second dryer stage the sludge steamfrom the first dryer stage to dry the sludge.
 5. The method of claim 3wherein the first dryer stage generates first dryer steam from waterevaporation from the sludge, and the second dryer stage has a firststeam carrier portion coupled to the first dryer stage and the firststeam carrier portion carries the first dryer steam adjacent to thesludge, and the second dryer stage has a second steam carrier portionisolated from the first steam carrier portion and the second steamcarrier portion carries the exhaust steam from the steam-poweredgenerator adjacent to the sludge, wherein heat from the first and secondsteam carrier portions dries the sludge moving therein.
 6. The method ofclaim 1, further comprising receiving in the condenser portion of thefuel dryer assembly exhaust steam from the steam-powered generator, andthe fuel dryer has a first dryer stage connected to the fuel inlet andhas a first heater portion coupled to the condenser and the first heaterportion evaporates a first portion of the water from the sludge withheat from the exhaust steam, and a second dryer stage is connected tothe first dryer stage and the second dryer stage evaporates a secondportion of the water from thickened sludge received from the first dryerstage with heat from the exhaust steam.
 7. The method of claim 1 whereinthe condenser of the fuel dryer assembly receives exhaust steam from thesteam powered generator, and the fuel dryer assembly having a singlestage dryer portion connected to the fuel inlet and adjacent to thecondenser portion, the single stage dryer portion evaporates water fromthe sludge using the heat from the exhaust steam in the condenser. 8.The method of claim 1 wherein the combustor portion is a fluidized bedcombustor assembly.
 9. The method of claim 1 wherein generatingelectricity includes generating electricity with a steam engine.